I'd only use 1 Truth, because I only run 2 Pashuul.
My rant on Truth: Truth is really only good early-mid game. Putting it at one copy and then hoping to draw it is going to be unlikely, and there's always that possibility that you've already used up all of your Pashuuls before you draw into/use Truth. While it's great when you can pull it off, I find it to be inconsistent at times and it can become a dead draw quite often.